Low loss tuning apparatus



tion but also of twice the mutual.

Patented Nov. 28,1944

Wendell'Lr Carlson, Haddonfleld, N. J., minor to Radio Corporation of America, acorporation of Delaware Application April 1; 1942, Serial No. 437,134

5 Claims. (01. rig-44) This invention relates to low loss tuning apparatus for ultra high frequency signalling systems.

It is known that a tuned section of a transmission line having a low power factor may be used in place of a. lumped capacitor and inductor as a tank circuit or tuner for oscillations of ultra high frequencies. Such tuners have many useful line tuner constructed in accordance, with the principle of the invention; and

Fig. 3 is a longitudinal sectional view of an alternate embodiment of the invention. 7 v

In the accompanying drawing wherein like reference characters designate the same or ourapplications. By way of example, it has previously been proposed to employ a timed section of atransmission line to stabilize the frequency of an oscillator, in which case it may replace a piezoelectric crystal in a transmitter operated with relatively high power output at very high frequency. The form of tuned line best suited for a tank circuit is one made up of two concentric conductors with the outer conductor completely closing and shielding the inner one. Thus, the power factor of the line as a resonant circuit is not increased by radiation or coupling to adjacent apparatus or circuits. Such tank circuits are usually constructed of copper, brass or the like and, when designed to handle relatively large currents, are quite ponderous and 1 hence occupy far more space than is desirable.

Accordingly, the principal object of the present invention is to provide a concentric line tuner which shall exhibit a high Q (0r f8-Ct0l' 0f merit), retain the advantages of a completely shielded dviceyand one which is nevertheless responding parts in all figures A designates the outer and B the inner concentric conductor of one section (A. B) of atuned line. The space between the concentric cylindrical conductors A and B is occupied by a second section of theline, 1 comprising an outer conductor C and an inner conductor D which are arranged in spaced rela-' ,tion, in the order named, about the central conductor B. These concentric conductors A, B, C and D are connected in series by means of end plates l, 2 and 3,,respectively, so that jointly they comprisethe inductance element of the circuit. Thus, the bottom" end plate i] connects the outermost cylinder A with the innermost cyl inder B. The innermost cylinder B is connected to the outer cylinder C of the second section (C,

D) by the end plate 2, while the outer cylinder C of the second section is connected to its inner cylinder D by plate I. It -will'be observed upon inspection of Figs. 1 and 2 that the plate 2 which serves to connect the innermost conductor 3 with the cylinder 0 is provided with a number (in tures 2a and that theadjacent end of the cylinder more compact than analogous prior art tuners. The foregoing and other objectsare achieved in accordance with the invention by utilizing the otherwise vacant space within a concentric line tuner to accommodateone or more additional series connected tuning section. Thus, the overall length of the tuner may be greatly reduced as compared withanalogous prior art tuners. Considered from one aspect the multi-cavity tun-' erof the present invention bears the same relanon to a single cavity tuner as a multi-turn Leon bears to a coil comprising a single turn, that is a to say, the total inductance in both cases is made up not only of the self-inductance of each secinductance between said sections. a

Otherobjects and advantages, together with certain preferred details of construction, will be apparent and the invention itself will be understood by reference to the following specification I and to the accompanying drawing, wherein Fig.1isatopplanview; V Fig. 2 is a longitudinal sectional view taken on the line 2-2 of Fig. 1 of a compact concentric gage complementary threads on the inner sur-f face of the outermost cylinder A. One. or more this case, six) of circumferentially arranged aper- Dis cutaway to provide a corresponding number of upstanding arms d which extend through said apertures, without touching the said plate 2. 1 These conductive arm-like extensions on the cylinder terminate in a conductive end plate 4 which is presented in useful capacitive relation across an intervening space to a plate 5 which closes the upper" end of the outermost cylinder B.

In the embodiment of the invention shown in Fig. 3, the capacitance between the end plates 4 and 5, and hence the tuned frequency of the device, may be varied by moving the top plate I with respect to the plate 4. For the purpose of making such adjustment the periphery of the said plate 5 is provided with threads It which enkeys K may be provided onfthe outer surface of the top plate 5 to facilitate its adjustment One or more insulated bushings (not shown) may be provided in the side walls of the cylinders A and C .for the insertion nectors.

From the foregoing it will be apparent that the ll present invention provides a multi-cavity tuner of appropriate circuit con-- possessing all of the desirable electrical characteristics of a single cavity tuner without any substantial increase in size.

What is claimed is:

1. A ,high frequency reactive device comprisinga pair of series connected outer and inner conductors mounted inspaced coaxial relation, and a second pair of series connected inner and outer conductors connected in series with said first pair and mounted in spaced coaxial relation in the space between the inner and outer conductors of said first pair.

2. A high frequency reactive device comprising a pair, of series connected outer and inner conductors mounted in spaced coaxial relation, a second pair of series connected inner and outer conductors mounted in spaced coaxial relation in the space between the inner and outer con- 3. electrical circuit comprising a nest of at. least four cylindrical conductors mounted in spaced coaxial relation, a plurality of end plates 4. The invention set forth in claim '3 and a wherein one of said end plates is movable .with

respect to another to vary the capacitance and hence the frequency of said circuit.

5. A resonant circuit comprisingat least four wENnaLL L. CARLSON. 

